The present invention relates to thermostats and more particularly to a novel form of thermostat for controlling the starting and stopping of a boiler, furnace, air-conditioner or for opening or closing of a zone valve for heating or cooling a building or a portion thereof.
Thermostatic temperature control is of course well known and is usually achieved by the mounting of a temperature responsive element on a wall in the area in which the heat is to be controlled, the temperature responsive element being so arranged that it will either open a circuit or close a circuit when a preset or selected temperature is reached. This, of course, is the type of operation which occurs in heating systems. The reverse type of operation may well be used in connection with air-conditioning or cooling systems.
The opening or closing of a circuit will then operate a particular heating unit in the case of temperature control under winter conditions; and, in the case of cooling systems, will operate particular valves in particular zoned areas of a building in order to achieve the desired cooling control.
Heretofore one of the problems in the arrangement of wall mounted thermostatic controls for temperature control systems is that the installation was required to be performed with accuracy and with a great deal of care, particularly in those instances where a mercury switch was used for such control. The levelling of the mercury switch type of thermostatic unit on the wall was extremely important to the accuracy of control and required extra installation time. This is because the calibration of the unit, with the lubber line stationarily mounted and the mercury switch rotatable, or vice versa, is gravity dependent and hence required careful levelling to assure that the set temperature and the control temperature were in fact the same. For example: a non-levelled thermostat might control at 80.degree. F when set for 75.degree..